PITTSBURGH — A former church youth worker pleaded guilty to possessing child pornography, including some depicting adults performing sex acts with infants.

Andrew Patterson, 46, of Monroeville must return for sentencing May 25 before a U.S. District judge when he’ll face up to 20 years in prison.

Patterson was a volunteer with the Living Waters Family Worship Center in Irwin and resigned his position there hours before his arrest in October 2014.

He was first charged by state authorities after an undercover detective allegedly traced porn he found on the Internet to Patterson’s computer.

Federal prosecutors took over the case and indicted Patterson two months later. He’ll remain jailed until his sentencing.

Patterson, his wife and daughter began attending Living Waters in the summer of 2014. By September, Patterson had persuaded the husband-wife pastors of the church to let him start a youth ministry, which had met weekly about five times before his arrest, according to Sylvia Tryon, one of the pastors.